Multiple Service Operators (MSOs) can offer a variety of services, including analog television (TV), digital TV, video on demand (VoD), telephony and high speed internet. MSOs can offer these services over a bi-directional hybrid fiber-coaxial (HFC) network utilizing optical fiber and coaxial cable. Bi-directional communications can be achieved through a forward path (e.g., downstream) and a return path (e.g., upstream). The forward path can be used to carry video, voice and data information from a MSO's master headend to subscriber homes. The return path can be used to carry control signals (e.g., VoD requests), voice and data information from subscribers' homes to the master headend of the MSO.
Optical fiber can be used to communicate information between a master headend and a fiber node. The fiber node can convert optical information to radio frequency (RF) modulated electrical signals to transfer information to subscriber homes through a coax based network. The forward path RF signals can represent multiple channels residing over a frequency spectrum (e.g., 50 MHz to 1000 MHz range). The fiber node can also convert return path RF signals residing on a frequency spectrum different from the forward path signals (e.g., 5 MHz to 42 MHz) for optical transmission to the master headend.
The Data-Over-Cable Interface Specification (DOCSIS) was established by MSOs to facilitate transporting video, voice and data packets over bi-directional HFC networks. DOCSIS originally was based on a return path frequency spectrum from 5 MHz to 42 MHz. More recent DOCSIS standards have increased the return path frequency spectrum (e.g., 5 MHz to 85 MHz) to provide additional return path channels thereby increasing return path bandwidth.